


Riding Training

by Lucy_Black



Category: Undertale
Genre: Ecto-Penis (Undertale), Ecto-Tongue (Undertale), Ecto-Vagina (Undertale), Incest, M/M, Vaginal Sex, ecto-body
Language: English
Status: Completed
Published: 2020-11-02
Updated: 2020-11-02
Packaged: 2021-03-09 04:02:15
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 6,725
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27338377
Author URL: https://archiveofourown.org/users/Lucy_Black/pseuds/Lucy_Black
Summary: It all started with the simple thought of trying to change Papyrus' "training" with Undyne.
Relationships: Papyrus/Sans (Undertale)
Kudos: 27





	Riding Training

When Papyrus arrived from his training with Undyne, Sans was already lying on the couch with his joke book inside the physics book planning his next performance at the Mettaton Resort.

-Hey, Bro! - Sans saluted, shifting his lights from the book to his brother.

Since the white painting of the battle corps was still immaculate and only a faint smell of burning and fresh tomatoes accompanied the arrival of the other skeleton, he supposed that the damage to the Captain's house was kept to a minimum (that and the fact that he arrived alone) .

-BROTHER! I SEE YOU HAVE ALREADY ARRIVED FROM YOUR “UNOFFICIAL JOB FOR THE SALE OF ILLEGAL AND LOW FOODS NUTRITIONAL RATE”!

-Sup, and how was the training with Undyne? - he folded a corner of the page he was reading (not that it really mattered, the next time he opened it it would be on a random page as he always did. That heightened the mystery and emotion of reading) and left the book on the pillow next to him.

-PERFECT, HOW COULD YOU EXPECT FROM ME, THE GREAT PAPYRUS! - The younger skeleton puffed out his chest and the red cloak he wore swayed in the still air of the room. - CAPTAIN UNDYNE SAYS THAT IF I CAN CONTINUE WITH THE GOOD JOB I WILL BE ENTERING THE GUARD IN RECORD TIME.

-How great, bro.

-YES, IN FACT SANS. TRUTHFULLY, IT WILL REALLY BE A NEW RECORD IN THE HISTORY OF THE GUARDA REAL, SINCE THERE WASN'T BEFORE A MONSTER SO SPECIAL THAT HAD TO BE TRAINED WITH CAPTAIN BEFORE. SO I AM GIVING EVERYTHING OF ME TO OVERCOME MY OWN NEXT BRANDS!

Sans just nodded, his smile fixed without moving an millimeter, not showing the slight displeasure he felt.

In particular, he hoped she would soon make him an official member, or at least a sentinel like him (to start with at least). Papyrus was perfectly capable of handling the job, and being realistic, what was the chance they would find a human? Minimal! And even if one did appear he was sure his brother could handle them (and he would guarantee that it was).

But that wasn't even what really pissed him off. He could understand and even be grateful for her concern for her brother's well-being and conscience, however ... wouldn't it be possible for her to try a little better excuse? Something not so useless when pretending that the cooking class disaster was some kind of training? (something that doesn't affect your meals?).

He knew that Papyrus did not need any combat training, his little brother was already at a level far above most monsters (even those of the Guard), but she could still train him in something, perhaps in the handling of a weapon (no that he thought his brother would want to participate in something as archaic as fencing, or ax throwing (bones were much more elegant and a classic in his own words).  
It would still be useless, but at least it would be better than pretending that destroying vegetables and setting the house on fire was some kind of training to become a guard (only if she expected Papyrus to capture the human by incapacitating him for food infection!).

While thinking about it he observed his brother who seemed lost in dreams of greatness and heroism. His smile softened a little when he saw the dreamy glow in the orbits of the other monster and he admired once again the pure glow that was his brother.

It didn't matter if they were literally in a shit hole, clinging to vain hopes of freedom, their brother was always ready to see the positive side of things, cheering and giving strength to anyone who needed it and that was what made his brother so precious to him (someone who was always smiling, but who had given up a long time ago).

He would sometimes like to hide it, keep it to himself, but Papyrus was like the sun, and like the star, it was impossible to countain him. 

Although he couldn't have he just for himself, he could bathe in its radiance in its privileged place as his brother. It was a pity that the other monsters could not see that greatness for what it really was (but a selfish part of him was happy that it was like this. With only him having the privilege of orbiting his personal star up close).

Putting his train of thought back on track, Sans considered, once again, how to try to influence Undyne another approach.

Perhaps he should try to suggest to his brother and let him influence the Captain. Papyrus was much more subtle and persuasive than he was. If he tried she was quite capable of taking it as an offense or dismissing it as a joke (sometimes maintaining the appearance of a relaxed guy had its disadvantages, like not being taken seriously by people definitely less informed than him).

But what kind of thing could she and her brother do together that would help Papyrus and not disturb the erroneous sense that the monster fish had about his brother? 

Papyrus was already good at trapping and fighting. What could be used to form a Royal Guard? (if he wanted Papyrus to do the job of convincing Undyne he would have to give something that made sense, after all Papyrus wouldn't be as lenient with him as he had been with the Captain).

Weapons was out. Combat, they already did from time to time. Traps were not Undyne's "beach". They already “studied” human behavior (Thanks to the Angel, Papyrus didn't take “specialized” knowledge seriously that Undyne had acquired from Alphys’s highly “reliable” manga).

-SANS? SANS!!!

-Hmm? Yes, bro? Sorry I think I dozed off for a moment.

-YOU WERE WITH OPEN ORBITS, SANS.

-Heh, heh. Incredible, isn't it? Soon I will be able to master the hability of walking while I sleep.

-THAT IS CALLED SONAMBULISM, BROTHER. AND I AM SURE YOU ARE BETTER TO KEEP THIS HABILITY "ASLEEP"!

Sans just smiled more while Papyrus glared at him.

-WHAT THOUGHTS ARE "WALKING" IN YOUR MIND BROTHER?

-Nothing Paps. Thinking is very laborious, besides, how would it be possible when I am a big hollow head? - and tapped the side of his skull for emphasis.

-NYEHHHH! SAAANS!

Sans laughed while the other monster stamped his feet in irritation. He loved to tease Papyrus.

The tall skeleton loved puns when he was younger, and even having a natural talent for them, but now he found them very childish and foolish. They weren't what a popular and cool guy would say, at least that's what Papyrus thought.

Sans had spent a lot of time trying to learn and follow his tastes (and he knew he sucked at it, the best he could do was be a joke on the line of “toc, toc” and rehearsed puns. Lucky for him that most monsters seemed having very weak standards for comedy so all the effort was not totally wasted and it ended up being useful as an unexpected source of income), so much so that now it has become something almost second nature. And despite all the supposed disgust with them, Sans knew that deep inside Papyrus still liked them (even though their jokes and puns are so weak).

All the feigned indignation was just adorable in Sans' eyes and he loved it when Papyrus just responded with his own puns (Papyrus was just too competitive. He couldn't help but show Sans what a comedy master really should be).

Papyrus sighed and stared at his brother. Sans shrugged and gave in.

-I was thinking about your training with Undyne.

Papyrus seemed surprised by his line of reasoning.

-SERIOUSLY? - his orbits widened and he raised his hands to his face - WOWIE! DON'T TELL ME THAT YOU FINALLY RESOLVED TO STOP BEING A LAZY ONE AND WILL JOIN US ?!

-Heeeee...no.

Sans could only shudder internally at the thought of accompanying those two in any form of training.

\- SO, WHAT DO MY TRAININGS HAVE WITH CAPTAIN UNDYNE?

-It's just... - he scratched his collarbone, uncomfortable - It's just that I thought it's a shame that his training is no longer... - he spied the other monster's expression and thought it best to proceed with caution - complete.

\- MORE COMPLETE? I MUST DISAGREE BROTHER. SURELY UNDYNE WOULD NOT LEAVE ANY IMPORTANT THING OUTSIDE OF OUR TRAINING. I CAN GUARANTEE THAT WE HAVE A COMPLETE, BRUTAL AND VERY HOT TRAINING, NYEH!

One of the orbits of the low skeleton contracted. It wasn't that he was really jealous, he was honestly happy that Papyrus had a friend, but the whole "tearing of silk" by the Captain of the Royal Guard was a little irritating. And it didn't help that the words "complete, brutal and very hot" denoted another context in his mind.

-Well... it's not like she could teach you everything bro. - he unconsciously let out a little poison.

-OF COURSE SHE CANNOT, SANS! EXCEPTIONAL AS UNDYNE IS, NOR SHE KNOWS EVERYTHING. BUT AS CAPTAIN OF THE ROYAL GUARD, AND A GREAT WARRIOR, SHE IS SURELY THE MOST WISE ON THE COMPLEX AND SUBTLE NEEDS FOR FORMING A ROYAL GUARD.

-Sure, bro. But it is that even Undyne may have limitations in this regard. - Sans persevered in his statement. Now that he had dug his grave, he was going to lie in it.

Papyrus looked taken aback. In her mind there was probably nothing Undyne couldn't do if she really wanted to (apart from opening the Barrier, of course), or anyone else in fact.

-I AM CONFUSED SANS. CAN YOU ELABORATE WHAT THESE LIMITATIONS ARE, BROTHER?

Sans froze. Okay, now what? He was just answering automatically, being driven by the simple desire to debunk the monster fish from any pedestal that Papyrus (and most of the Underground) put she on. But now that Papyrus was not defending her blindly, but really willing to listen to his argument, he found himself without one.

Dammit! And that would be the perfect cue! A crack to give something that his brother could work with Undyne after. But the problem is that Sans had no idea what to suggest.

The truth is that now his mind was only able to conjure up images of what Undyne could not teach his brother, and none of his ideas was something that he wanted his brother to try to influence Undyne to try (not that he thought his brother or herself Undyne was willing to do it).

Images of his brother bent over the couch, while Sans tested which which fund could go. Or Papyrus on him, riding him and seeing how many "squats" he would do on his penis, before surrendering.

The image burned in his mind and made his magic stir.

-I AM WAITING, SANS!

-One moment Paps, I'm riding, I mean... - Sans was dragged from his fantasies. 

He frozed for a moment, his mind racing to try to get back to the current problem (or problems if he counted his penis wanting to come up to get into the conversation).

As if by miracle an idea came up. It wouldn't solve his problem with Undyne (far from it, but he could think about it later), but it would solve the current ones. He stuffed his hands in his pocket as he sank deeper into the couch and quickly ran his line of action.

-Well... you see ... there is not the necessary for her to teach you everything there is to be a Royal Guard.

-I AM SURE THAT CAPTAIN UNDYNE IS MORE THAN ABLE TO ACHIEVE WHAT IS NECESSARY FOR THE GOOD OF THE ROYAL GUARD.

-Yes, but even she would have difficulty getting some horses.

-HORSES?! - Papyrus asked in disbelief. Apparently Sans had managed to catch him completely off guard this time.  
-Yes, in the past there were guards mounted... you know... knights... - he let his voice die and waited for the reaction.

Papyrus' orbits sparkled with enchantment and Sans can see the exact moment your brother began to see himself on a horse, shining armor, hair in the wind, riding towards sunset (even though Papyrus had no hair and he had never seen one sunset in your life).

-WOWIE! KNIGHTS! THAT WOULD BE AMAZING!

-Yes, but unfortunately we don't have any horses... unless you try to convince Aaron to give him a ride.

He only took it as a provocation, he knew that Payrus would never do such an impolite thing, even though Aaron would probably be more than happy to serve as a “mount” for any monster (and he wasn't just talking in sexual terms).

He watched his brother, quickly planning the next step. He tried to appear as nonchalant as possible while continuing.

-Of course, we don't have horses, but I think it's a waste that Undyne doesn't give a training to... you know... when we get to the surface.

Even though he was discouraged, Papyrus was quick to jump to his friend's defense.

-AND HOW DO YOU EXPECT SHE TO TRAIN ME, IF YOU EVEN SAID WE DON'T HAVE HORSES?

-Oh, we don't have humans either, and that doesn't stop us from making traps for them.

Papyrus' orbits widened.

-YOU HAVE REASON, SANS! JUST BECAUSE WE DON'T HAVE HORSES DON'T MEAN WE CANNOT TRAIN! BUT THEN WHY ISN'T SHE TRAINING ME TO BE A KNIGHT ALSO?

He looked distressed, perhaps fearing that Undyne didn't trust or think he was so great or worthy of his riding lessons. Sans had to remedy such erroneous thoughts immediately.

-She probably thinks that a guy as nice as you doesn't need this training. You are so amazing bro, you sure already know how to do it.

-BUT OF COURSE! I, THE GREAT PAPYRUS, AM A MASTER IN EVERYTHING THAT REFERRES TO THE ARTS OF THE ROYAL GUARD. NYEHEHEHEHEHEHE.

Papyrus swelled again with confidence, the little doubt forgotten as the little slip it was.

Sans smiled waiting. The fish had already taken the bait, just wait for the tug that was coming.

-YES THE MAGNIFICENT PAPYRUS, FUTURE GUARDA REAL, WILL BE THE GREATEST KNIGHT THAT THE GUARD HAS ALREADY HAD!

-Sure bro.

NO ONE WILL EXCEED MY ASSEMBLY SKILLS!

-Of course not.

-BUT... - Payrus hesitated and Sans refrained from smiling greedily like a shark that feels blood in the water. - EVEN THE GREAT PAPYRUS NEEDS A SOME PRACTICE, A... TRAINING NOT TO RUST HIS MAGNIFICENT SKILLS.

Bingo! Now I just had to pull the line.

-Of course Paps, and if you want I can help you with that.

-BUT IT'S OF COURSE... WAIT, YOU CAN? - The tall skeleton was interrupted by pure shock and faced his brother with wide orbits.

-Yes.

-And are you willing to do that? - He asked suspiciously.

-For my super cool little brother? Of course yes - shrugged.

Papyrus stared at him, squeezing his orbits suspiciously. He measured Sans and analyzed his words for any hidden pun or joke. Sans waited patiently for the verdict.

-OKAY. I THE GREAT PAPYRUS WILL AGREE THAT YOU HELP ME WITH MY MOUNTING TRAINING. BUT I SHOULD ALERT YOU, WITHOUT WHOOPIE CUSHION!

-Ow Bro! So you hurt me. - Sans jumped up from the couch - Then? Do we start now?

Papyrus could even continue to look at him suspiciously, in any situation Sans would wind and delay indefinitely any greater attitude that exists, so having applied to help with a training and still wanting to start immediately would seem very suspicious (or a miracle), but he was very excited to be able to learn something new, and show them off to Undyne later, to care.

-YES! I AM ABSOLUTELY READY! SHOULD WE GO OUT?

-It will not be necessary, since we will use the least magic, we can do it at home.

Paps pouted. He, like Undyne, was a big fan of great (explosive) magical displays in his training.

-Your room will be perfect for that.

-SO LET'S GO!

As Papyrus climbed the stairs, his long legs eating quickly from a distance, Sans turned the other way and headed for the front door. As soon as Papyrus opened his bedroom door, he found Sans waiting for him inside. The young skeleton didn't even blink, more than accustomed to his older brother's adventures.

Closing the door and standing in the center with his hands on his hips, he faced the smaller monster.

-And THEN WHAT SHOULD I DO FIRST?

-How about taking out the battle corps? - he suggested trying to contain the greedy tone of his voice.

-WHAT?! BUT HOW CAN I TRAIN WITHOUT HIM? A GUARD IS ALWAYS READY FOR BATTLE!

Without missing a beat Sans replied.

-But you have to learn to balance yourself and his weight can destabilize you.

-NONSENSE!! MY BALANCE SKILLS ARE SUBLIMES AND ENVYABLE! BEYOND THIS, SHOULD I NOT LEARN TO RIDE WITH HIS WEIGHT?

Your brother was incredible, but sometimes his brilliance could be a hindrance. He thought quickly about how to get around this problem.

-But it can be complicated for the poor horse... what if we don't have the right equipment? Your battle corps can hurt him.

Papyrus choked.

\- YOU ARE COMPLETELY RIGHT BROTHER! I SHOULD THINK ABOUT MY PARTNER'S WELL BEING ABOUT EVERYTHING!

And he started to remove the armor/costume they had made. 

Sans blessed Papyrus' good nature. It might be a little low to appeal to your kindness and concern for the welfare of others, but as they say: in love and war anything goes!

As soon as he got rid of the battle body, guarding it in the closet, he returned only wearing the date clothes he always wore underneath his costume (minus the hat that, since he wasn’t on a real date, he didn’t need to use to hide his special spaghetti dish). 

Seeing the short top that comfortably covered his ribs, Sans had a brilliant idea. Giving himself a mental pat, he pulled out his computer chair and sat down.

-Hum... Paps if you are concerned with training with the weight of the battle body, we can simulate that.

Papyrus looked at him expectantly.

-You just need to conjure your "other" body and match it to the weight of the armor.

-Oh! - their orbits started to fill with stars again - VERY WELL THOUGHT SANS!

-Heh, thanks bro.

Sans should feel bad about taking advantage of his brother's weaknesses, but he was a dirty monster and had already resigned himself to it (besides, if it was any consolation for that part of him that was still conscious, he would guarantee that Papyrus would enjoy in end).

Papyrus closed the orbits and like (heheh) magic, the outline of a curvaceous body began to emerge. It was like the image of a ghost, but instead of disappearing, it appeared.

First the clothes swelled and then the transparent outline, like heat vapor, which gradually gained more solidity and color. Soon it ceased to be just an illusion to become a real, curvaceous body with a semi-translucent orange color.  
Papyrus opened his eyelids and looked down appraisingly. Her breasts had decently filled the “Cool Dude” shirt, without being pressed against it (thanks to the malleable fabric), the same could not be said of the shorts that were adjusted to a bony hip and now tightened their ecto-hip in a way that it sure was uncomfortable.

-I think you better take off the short, Paps. - Your plan was going smoothly.

-NONSENSE! I CAN TAKE A LITTLE DISCOMFORT! BEYOND, IF I TAKE IT OUT, I WILL HAVE LESS WEIGHT. I AM A MONSTER OF HIGH STANDARDS BROTHER. I CANNOT ALLOW EVEN MORE INEZATIDITY!

Sans scratched his skull. He calculated that the garment only counted on a few grams, but his brother was too detailed. Oh well, he would just have to keep winding it up.

-Hum... yes I understand, but it would be better for you to be more comfortable for that first workout.

He could put that aside for now if Papyrus continued to be stubborn, but he thought that if he let it go later Papyrus might be even more reluctant to do it, and for his plan to work he needed the shorts to come off in a way or another,

\- Why don't you take them out and recalibrate then?

Papyrus scratched his chin thoughtfully. In what seemed like a mental shrug (maybe the shorts were really bothering him after all) he relented, unbuttoning the shorts and pushing them down.

Sans followed with bright lights as more of his brother's body was revealed.

Papyrus fished his shorts off the floor and carefully folded them, placing them on the end of the bed and turning to Sans without an ounce of shame. Not that he should have any. Payrus was perfect (and he knew it), and modesty was a concept for fools who were unsure or who did not know their own greatness.

Sans let his eyes roam over his flat stomach, his hips smooth, to the "v" in the center and the firm thighs that framed him. He restrained the desire to lick his teeth and continued with the instructions.

-You may want to take off your shoes too - and before your brother protested he completed - or you can keep them if you don't mind stepping on your sheets with them.

The monster looked at his sneakers and the immaculately clean sheets. It was true that they were always inside in the boots and therefore were clean, but it was the intention that counted. With a sigh he sat and untied them, leaving them at the foot of the bed.

\- THE STOCKINGS STAY. - He commanded and Sans shrugged nonchalantly.

-Now just rebalance the weight...

-AH! SURE.

And in a second the breasts that were only slightly tightened by the shirt, were stretching it out. Sans felt his mouth fill with saliva. He thought of suggesting that he take off his shirt too, but thought he would be pushing too hard. Not to mention that Papyrus was already looking at him with that look of "Dare to finish that pun!" and while it was a very hot look, it was not time to antagonize him.

-Great. Now sit on the bed.

Papyrus obeyed, sitting with his legs together on the edge of the bed and waited in lively expectation. 

Sans finally got up and went to the other skeleton while taking off his gloves, putting them in his pocket, and pulling out a bottle from inside the other pocket. He stopped in front of Papyrus and opened the bottle.

-Now Paps, when you go riding a horse you will luckily have all the necessary equipment, but since unforeseen events happen, and as we obviously don't have a real one here, we will improvise.

Papyrus listened eagerly, drinking Sans' words with almost childlike delight, without even questioning how or why Sans would know anything about riding horses.

He opened the bottle and poured a few drops on Papyrus' thighs.

-WHAT IS IT?

-Almond oil.

Papyrus frowned.

-And WHAT'S IT FOR?

-Your security. Mounting can be harmful to sensitive parts and how you are using your ecto-body without protection... we don't want accidents, do we? 

Papyrus emphatically agreed. Taking care of yourself and your equipment was an integral part of being a good guard.

Sans closed the bottle and put it away. Extending his hands, he began to spread the oil on Papyrus's thighs, who watched everything with curious eyes, but without questioning again. Sans spread the oil from the hip to the knees with smooth movements, taking care to tighten areas that could be more sensitive.

-Separate them a little Paps. I need to spread it well, especially inside to avoid friction burns.

Papyrus nodded and parted his knees, letting Sans work. He continued to spread the oil, now on the inside of his thighs, taking care not to touch where he wanted it most, at least not yet.

He soon noticed the moisture arising between the lips. Perfect! That way he wouldn't have to worry about using more oil.

He took his hand there and tried to massage it as clinically as possible. It was an arduous task to try to remain impassive when feeling the heat and humidity that had nothing to do with the oil. 

He soon withdrew his hand, not wanting to ruin his plan by being flustered, but he did not contain his satisfaction at feeling, rather than seeing, the slight twitch of his aborted hip, trying to chase his hand. A quick look up and Sans could see that it wasn't the only thing "cheering up" there.

He straightened up and took a step back looking at his brother sitting on his a red racing car bed , his bare legs spread slightly leaving his pussy shyly showing. Her top stretched with the full breasts he had conjured and enlarged, her face confident and slightly flushed, her orbits bright with expectation.

He felt his determination almost weaken at the urge to dive between those thighs and get a taste of the other skeleton, but he controlled himself and turned to face Papyrus in his orbits.

-Ok Paps, now get on your knees in bed.

Papyrus was quick to obey. As the bed was single (and Papyrus had long legs) he positioned himself so that he was facing the back of the car (or where the headboard would be). Sans climbed back, without having to worry about shoes, as his slippers fell softly when he went up (and his socks were almost dry after all).

He positioned himself on his knees behind Papyrus and pushed his shoulders a little so he could sit on his thighs (and he could be more at his level).

-Spare the thighs a little more, Paps. Horses are big creatures.

-I KNOW WHAT A SANS HORSE IS! EVEN IF YOU'VE NEVER SEEN ONE!

-Ok, sorry Paps. 

Despite the protest Papyrus separated his thighs. Sans wouldn't know the size of a horse either, but that didn't matter. He stroked Paps' shoulders (or what the basketballs didn't cover).

-Now comes the difficult part Bro. You have to visualize the horse and pretend to be riding it. The key is in the thighs, in the movement. You have to tighten them to keep the animal between them and follow its movements so as not to fall.

Papyrus made a scornful sound.

-THAT'S EASY, BROTHER! I COULD MAKE IT BLINDFOLDED... WHICH WOULD NOT MATTER, SINCE I AM NOT SELLING A HORSE EVEN!

Despite the guarantees, Papyrus took a few seconds to move. He flexed his knees, lifting and lowering yourself.

Taking into account Sans' weak explanation, who had no idea what he was talking about, just trying to turn his wishes into something that would look like a riding lesson (if we took into account all the sexual metaphors with riding he imagined that it should have some resemblance to the act itself), he seemed to be following exactly what Sans had tried to say (not that it mattered, as far as Sans knew, it could be like that even if were riding a horse).

-Very well Bro! - He ran his hands over his arm encouraging him. - Stroking the bone before going up to the collarbone and squeezing the bones gently. - You're doing great Papyrus.

-OBVIOUS! I AM AN EXPERT IN THIS, BROTHER. NO ONE WITHIN THE ROYAL GUARD WILL BE A KNIGHT LIKE ME!

Sans smiled and ran his hands over his back as he encouraged and enjoyed the sight of that upturned ass swaying with the up and down movements. He ran his hand down the side of his ribs to the front where he started to massage the part under her breasts. When a hand up and squeezed one, Papyrus froze.

-HUM... BROTHER?

-Yes, Bro? - Sans asked innocently.

-WHAT...? 

Sans gave another squeeze before circling the nipple with the tip of his finger.

-Relax Paps. You are very rigid. You have to relax... - the other hand held his bare hip and indicated that he should continue with his "training". Papyrus followed the lead, still a little hesitant. - You mustn't be so stiff, bro. You have to keep pace with your horse... Relax ...

Papyrus looked forward and took a deep breath, letting out the shaky air when another finger joined the first and pinched the hardened nipple causing the younger skeleton to rise in what would have been a jump, if it was not already kneeling.

-Heh! Well, it looks like you jumped a pebble on the way, huh? - He said rotating the nipple between thumb and forefinger. The tall skeleton grunted, but Sans thought the sound sounded more like a disguised groan than a sound of irritation.

With one hand playing with a breast and the other on his hip, Papyrus found a rhythm again, but now less stiff and less lift and more swinging. 

Sans licked his teeth and continued to enjoy the view and to handle, more and more rudely his brother's breast. When he started to hear Papyrus gasp and the little sketches of moan escape between his breaths, he gave his breast a last squeeze and pulled away.

-I think it's enough training for today.

-WHAT?! - Papyrus froze and turned his face in horror. - NOT! THE GREAT PAPYRUS CAN CONTINUE! THAT... THAT WAS INSUFFICIENT!

"Insufficient, huh?" Thought fun.

-I don't know Paps. You're doing great, but it looks like you're getting tired... I don't want to wear you out in a first workout.

\- FOOLISHNESS!!! GREAT PAPYRUS ISN'T EVEN SWEATING!

Sans scratched the back of his neck, pretending to hesitate.

-I don't know Paps... the next lesson can be a little heavier and...

-I CAN HANDLE IT!!

Sans hid his smile.

-Ok, Paps. So wait a minute. In the meantime, close your eyes and visualize your mount. You know that visualization is an important part of any workout.

-HUMPFT! SURE I KNOW! I ALWAYS VISUALIZE MY MAGNIFICENT SPAGHETTI PLATES WHILE PREPARING IT.

"hat's why they always end up half burned". Sans completed it mentally.

While Papyrus closed his sockets and his expression wrinkled in concentration, Sans got out of bed and got rid of his shorts, dropping her anyway on the floor. A small sigh of relief escaped at last having his cock free. 

Taking himself in one hand, he pulled the oil bottle out of his pocket and dropped it a little on his penis, he smoothed his a few times, spreading the oil and pre-semen as he watched your little brother's vision with hunger.

Papyrus remained with closed orbits, focused on his visualization of a horse (or so Sans thought), but all the concentration did not erase the slight flush on his cheekbones, the tension in his shoulders, the straight spine that only highlighted his breasts more heavy and the nipples erect as if they wanted to cross the cotton barrier. Sans could almost see their orange shadow through the shirt.

His eyes wandered lower, to his firm stomach and hip that was being asked to be squeezed by his fingers. He had to squeeze the base of his cock and bite the moan that almost escaped him when he noticed the small orange splashes on the bed coverlet. He ran his tongue over his teeth again, imagining walking with the small trail that ran down his tense thighs to the fountain in the middle of them.

He sat across from Paps and carefully tucked himself between his open knees. Sans squirmed a little lower until his groin matched the other skeleton's waist. From this angle he could see the glow of Paps's arousal brighter than the oil he had spread. Once again he had to force himself not to slide anymore and make Paps ride his face, but he had plans and he was not going to deviate from them.

-Ready Paps.

Papyrus opened his orbits and looked at him.

-SANS! DON'T TELL ME YOU'RE GOING TO TAKE A NAP NOW, YOU LAZY!

-Hah, no Paps, I'll help you with training.

-SERIOUSLY? - He asked excitedly.

-Of course Paps, all for my nice little brother. Are you ready now?

-OF COURSE! I WAS BORN READY SANS!

"Truth." thought fun.

-Now, Papyrus, get down a little.

-BUT I AM HEAVY BROTHER.

-Nah! You're just bon...

-DO NOT YOU DARE!

-Heh, heh.

With one hand to steady himself and the other to guide Papyrus he made his brother duck. When the tip of his cock touched Papyrus' pussy, he stopped.

-It's okay, bro. It's just... something to keep you connected to me... like... like... a seat belt! 

(Heavens, even he couldn't believe such an excuse! But what could he do? His mind was focused on other things at the moment).

Pleased by Sans' assurances, Papyrus slowly sat down again.

"Fuck!! He was so tight!"

He made Papyrus go slowly (so much for not having prepared him as he should, so much for giving him time to better enjoy the sweet feeling of having his little brother squeeze him so deliciously).

Papyrus slowly lowered himself, rising a little, then lowered himself a little more, in a slow parody of the movement of a few minutes ago. 

Despite what he had said before, small orange droplets began to appear through his skull with the effort and small sighs punctuated his breath.

When Papyrus reached the last stretch, Sans helped by pressing Papyrus down with both hands on his hips. Papyrus stopped, panting. His thighs tightening around Sans, and whether it was the effort he had been making or the pleasure, Sans didn't know.

Sans let him rest for a moment (he needed it too if he didn't want to burn the start). Closing his eyelids to enjoy his brother's velvety walls pressing him.

-Very good, Paps! You are doing so well! Amazing. A true master. - He showered praise as he felt Papyrus twitch around him before relaxing.

Papyrus looked up and smiled proudly.

-All right, Paps? - He asked to be sure.

Papyrus did not respond immediately. He contracted his hips and tightened his pussy around Sans's cock, testing as if to see how well filled it was.. Sans bit out a moan at the small artful movement. 

The younger skeleton straightened up before speaking.

-YES, OF COURSE! NO CHALLENGE IS TO BIG FOR THE AMAZING PAPYRUS. NOT EVEN A SEAT BELT FOR HORSES!

Sans had to hold back the hysterical laugh that threatened to come.

-I knew you would get Bro ...- while talking he caressed Papyrus' belly and went down to where they connected. He nudged until he felt the swollen button on Papyrus's clitoris and stroked it gently. Her little brother shuddered violently and pressed himself against his finger.

-Ready brother?

\- ALWAYS SANS!

Sans started to move his hips and Papyrus followed him, at first it was a little difficult to coordinate the movements, but Papyrus was a quick student and within moments he was riding his penis like the professional he claimed to be.

Sans was in the clouds. Contrary to all his reputation for being a lazy born, Sans did not leave all the work to his brother. At first he dictated the rhythm, lifting his hips with precision and vigor, but as Papyrus gained confidence and imposed the canter rhythm, Sans relaxed on the bed enjoying his brother's show so lovingly riding his cock and the show a part that were her breasts, which even confined, swaying in equal measure.

He lay there, just watching until the desire was too much to contain. He then couldn't resist any longer and pushed the offending piece of fabric to reveal the longed-for view of Papyrus's breasts.

Now that they were free it was as if they had a life of their own, bouncing beautifully in front of them. “Ah! Now, ”he relaxed on the bed and let his brother“ train ”as he liked while enjoying his private show.

Papyrus at first was silent, only his labored breathing betrayed his efforts, but as he increased his rhythm small moans and wails escaped through half-open teeth.

He had made a move to grab Sans' dirty sweatshirt at first, but then he restrained himself, determined to keep himself straight and without the help of support (later Sans would realize he was trying not to hold on to the “horse”, trying to keep his hands free in case he need them for an attack, even if they were not needed for a magic attack, not your little prodigy brother).

Sans continued to shower praises to his brother, saying how amazing he was, how handsome he was, how tight he was...fuck Papyrus ...

Only the sight of his brother, completely undone, his self-control (which allowed him not even to sweat in combat) completely undone, was enough to make him come. It was only his willpower that kept him at bay. The desire to continue to see him, to continue to feel him, a little more, just a little more.

He followed a trembling drop of sweat running between his heavy breasts, breasts bouncing so beautifully, the nipples hard and shiny with exertion. He had to stop his vocalization to swallow, and it was only Papyrus' weight that stuck him to the bed, otherwise he would have bent, stretched, scaled, whatever was necessary to have one of them in his mouth. Feel your weights in your hands and the taste on your tongue.

Papyrus groaned loudly and Sans looked back at his face. The younger skeleton had closed its orbits tightly and its jaw was moving as if it were speaking despite only sighs and occasional moans escaping through it. The older skeleton realized that the younger man's entire body had tilted slightly towards him and he raised his skull a little, as if the proximity would make him hear those unspoken words.

Perhaps sensing Sans' movement, Papyrus opened his orbits and faced his brother. The sight took off a tremulous request.

-SA-SANS... SAAANS ...

It was just his name, but it was enough to break the short skeleton. Her hands flew to Papyrus's hips and squeezed him, forcing him down as he raised his own with renewed vigor.

Papyrus gasped at the sudden movement and leaned closer, closing his eyes and enjoying the new angle.

It only took a few more strokes for Sans to reach his peak and surpass it, with a hoarse sound from the back of his throat. He closed his orbits enjoying the sensation of those velvety walls contracting around him as he came in hot surges inside his little brother.

He blinked back to himself to feel Papyrus still rocking against him, making little desperate and needy sounds. He released one hand and guided it to the point where they connected. 

He didn't have much coordination, still very drunk from pleasure, but he didn't have to work hard. Papyrus was still riding him with intensity and every time he came down he hit Sans fingers and that little stimulation was enough for him to reach his orgasm too.

Sans moaned helplessly when he felt his brother squeeze him like an addiction, after his own orgasm the sensation was exquisitely painful. He only realized that he had held his breath when he started breathing again while Papyrus finally relaxed around him and collapsed on him, wheezing more than (heh, heh) a racehorse.

Sans closed his orbits and let his lazy smile widen. With a hand that hadn't been caught between their bodies, he stroked Papyrus's back, feeling him still tighten around him and the pressure of her breasts crushing his ribs.

They were silent except for their calming breathing and Sans' hand that lazily stroked Papyrus's spine. When the breathing of the younger skeleton stabilized, long before Sans', and he stopped massaging his over-stimulated cock still inside him.

The tall skeleton moved up on its elbows and faced Sans.

-BROTHER?

Sans only opened a crack in an orbit, he was almost asleep.

-Hn?

-I THINK I'LL NEED MORE MOUNTING TRAINING

This made Sans wake up and face his brother who was looking at him with a bright smile and malicious orbits. Papyrus gave the softened limb still a playful squeeze still inside him, and Sans could only choke on the pain-pleasure that shot through him like lightning.

"Where the hell did I go to tie up my mare!"

It was his last thought before Papyrus leaned over and kissed him.

**Author's Note:**

> Just to be clear, Papyrus knows exactly what his brother is planning, but if Sans wants to play, who is he to waste his lazy brother's effort?
> 
> Thanks for reading!


End file.
